• 열처리공학회지
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• 제20권5호
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• pp.243-249
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• 2007

The age hardening behavior and mechanical properties of an extruded Al-Zn-Mg-(Cu)-0.1 wt.%Sc alloy were investigated with the Sc addition and ageing temperature. The results showed that the $Al_3Sc$ compounds were formed by Sc addition and distributed preferentially along the extrusion direction. The age hardening of Al-Zn-Mg-Cu-0.1 wt.%Sc alloy which was treated by T6 process was more significant than that of Al-Zn-Mg-0.1 wt.%Sc alloy. The tensile property of Al-Zn-Mg-Cu+0.1 wt.%Sc alloy was also higher than that of Al-Zn-Mg-0.1 wt.%Sc alloy, which is 691 MPa and 584 MPa in strength and 9% and 11% in elongation, respectively.

• 열처리공학회지
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• 제19권5호
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• pp.257-261
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• 2006

Scandium(Sc) in Al-Zn-Mg-Cu based Al alloy on precipitation phenomenon was compared to a 7001(Al-7.2%Zn-3.2%Mg-1.8%Cu) Al alloy. GP zone and ${\eta}^{\prime}$ phases were the main strengthening phases at low aging temperature under $100^{\circ}C$, but ${\eta}^{\prime}$ and $Al_3Sc$ phases were the main strengthening phases at high aging temperature above $1600^{\circ}C$ in Sc added 7000(Al-7.7%Zn-2.0%Mg-1.9%Cu-0.1%Zr) Al alloy. With the addition of 0.1%Sc in 7000 Al alloy, the activation energy for the GP zone, ${\eta}^{\prime}$ and ${\eta}$ phase decreased compared to the 7001 Al alloy. This result indicates that the Sc accelerated the precipitation for the GP zone, ${\eta}^{\prime}$ and ${\eta}$ phases in 7000 Al alloy. Al-7.7%Zn-2.0%Mg-1.9%Cu-0.1%Zr-0.1 Sc alloy has higher strength than 7001 Al alloy, which has high strength.

• 비파괴검사학회지
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• 제31권1호
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• pp.32-39
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• 2011

본 연구에서는 Cu와 Cu-Zn 합금의 저주기 피로 동안 발달한 전위 하부조직의 변화를 비파괴적으로 구분하고 평가하고자 하였다. 비파괴시험으로 초음파속도, 전기비저항 그리고 양성자소멸시간을 측정하였다. 서로 다른 적층결함 에너지를 갖는 Cu와 Cu-Zn에 대해 반복피로시험을 수행하고 이들 재료에서의 전위거동과 비파괴평가 파라미터와의 상관성을 연구하였다. Cu는 전위셀 하부구조를 형성하였지만, Cu-Zn 합금은 피로 사이클에 따라서 전위밀도는 증가하고 단지 평면배열의 전위구조를 형성하였다. 상온에서의 반복적인 피로에 의해 발달한 격자결함인 전위와 공공으로 인해 초음파속도의 감소, 전기비저항의 증가 그리고 양성자 소멸시간이 증가하였다. 비파괴평가파라미터의 지속적인 변화를 보이는 평면배열의 전위구조를 갖는 Cu-Zn에서와 달리, Cu에서는 전위셀구조가 발달하면서 더 이상의 큰 변화를 보이지 않았다.

• 한국주조공학회지
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• 제29권6호
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• pp.265-269
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• 2009

The optimum RRA heat treating conditions and SCC (stress corrosion cracking) resistance of semi-solid Al-Zn-Mg-Cu alloy fabricated by inclined cooling plate were compared with those of conventional mould cast alloys. The non-stirring method characterized by using a cooling plate can effectively eliminate dendritic structure and form a fine globular semisolid microstructure in as-cast Al-Zn-Mg-Cu alloy and the SCC resistance of semi-solid Al-Zn-Mg-Cu alloy was higher than that of conventional mold cast alloy. Also, after retrogressed treatment at RRA heat treatment of semi-solid Al-Zn-Mg-Cu alloy, retrogressed treatment time has increased more than 10 minutes at $180^{\circ}C$ to recovery the T6 heat treatment strength.

• 한국재료학회지
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• 제5권6호
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• pp.682-689
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• 1995

Mg-Zn합금계의 입자미세화를 위하여 0.5-6 wt.% 조성범위의 Cu 및 Si를 첨가하였다. 합 잉곳트는 4 $\times$ $10^{-4}$ Torr의 진공의 BN을 내벽에 바른 석영관내에서 제조하였다. 제조된 합금을 435$^{\circ}C$에서 8시간 용체화처리한 후 결정립크기와 경도를 측정하였다. 측정결과 Mg-6wt.%Zn합금의 입자미세효과는 Cu가 2wt.%첨가될때, Si은 1.5wt.%가 첨가될 때가 최적의 조건이었다. Mg-6wt.% Zn과 Mg-6wt.%Zn-2wt.%Cu 및 Mg-6wt.%Zn-1.5wt.%Si합금을 시효열처리하여 시효거동을 조사하였다. 입자미세화에 의한 경도증가효과는 Mg-Zn-Cu합금계에서 크게 나타났으며 시효에 의한 경도증가 효과는 Mg-Zn-또합금계에서 크게 나타났다.

• 한국주조공학회지
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• 제35권4호
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• pp.67-74
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• 2015

In this study, Mg-Zn alloys are investigated in terms of their thermal properties after an addition of Cu. Al element is added to improve the mechanical properties and castability in general case. However, it was excluded here because it significantly decreases the thermal conductivity. On the other hand, Zn was added as a major element, which had less influence on reducing the conductivity and can complement the mechanical properties as well. Cu was also added, and it improved the heat transfer characteristics as the amount was increased. The composition ranges of Zn and Cu are 6 wt.% and 0~1.5 wt.%, respectively. Mg-6Zn-xCu alloy was prepared by a gravity casting method using a steel mold and then the thermal conductivity and the microstructure of the as-cast material were investigated. By measuring the density_(${\rho}$), specific heat_(Cp) and thermal diffusivity_(${\alpha}$), the thermal conductivity_(${\lambda}$) was calculated by the equation ${\lambda}={\rho}{\cdot}Cp{\cdot}{\alpha}$. As the amount of Cu increased in the Mg-6Zn-xCu alloy, the heat transfer characteristics were improved, resulting in a synergistic effect which is slow when the added Cu exceeds 1 wt.%. In order to investigate the relative thermal conductivity/emission of the Mg-6Zn-xCu alloy, AZ91 and AZ31 were experimentally evaluated and compared using a separate test equipment. As a result, the Mg-6Zn-1.5Cu alloy when compared to AZ91 showed improvements in the thermal conductivity ranging from 30 to 60% with a nearly 20% improvement in the thermal emission.

• 한국주조공학회지
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• 제30권4호
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• pp.137-141
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• 2010

The effects of Zn amounts on the castability and tensile properties of Al-Zn-Mg-Cu alloys were investigated for development of high strength die casting aluminium alloys. Al-Zn-Mg-Cu alloys with 3.5% Zn showed high cast cracking tendency and poor mold filling behaviour. Al-Zn-Mg-Cu alloys with 5wt% Zn and 7wt% Zn had the tensile strengths of 300~400MPa and the elongations of 2~18%. The effect of Zn on the tensile strength of Al-Zn-Mg-Cu alloys was insignificant, but Al-Zn-Mg-Cu alloy with high Zn amount had lower elongation.

• 한국기계기술학회지
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• 제20권6호
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• pp.818-823
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• 2018

In this study, the effect of pre-aging treatment for inhibition of natural aging of Al-4.8Zn-1.3Mg alloy by extrusion process was investigated. Firstly, the as-cast microstructure of Al-4.8Zn-1.3Mg alloy billet and its evolution during homogenization($460^{\circ}C$, $4h+510^{\circ}C$, 5h) were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), hardness analysis. The as-cast microstructures of Al-4.8Zn-1.3Mg alloy reveal $Mg_2Zn$, $Al_5Cu$, $Al_{13}Cu$ formed between dendrities. After homogenization, MgZn, $Al_4Cu$, $Al_{13}Cu$ phases precipitated into the matrix. In addition, standard deviation of homogenized billet was improved than as-cast billet from 2.62 to 0.99. According to pre-aging($100^{\circ}C$, 1h) Al-4.8Zn-1.3Mg alloy by extrusion process, yield strength and tensile strength deviation improved more than condition by natural aging.

• 한국주조공학회지
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• 제22권2호
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• pp.82-88
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• 2002

Al-5.5Zn-2.5Mg-l.5Cu semi-solid slurry was prepared by cooling the liquid metal with a low superheat to a solid and liquid co-existing temperature. Relatively round solid particles could be obtained in the slurry through the simple process. The prepared slurry was deformed into the metallic mold by a press and the mechanical properties of obtained specimens were investigated. Mold filling ability of the alloy slurry was also investigated and compared with that of A356 alloy. Al-Zn-Mg-Cu alloy showed lower mold filling ability than A356 alloy probably because small amount of eutectic phase is present and the heat of fusion generated during solidification is smaller than that of A356 alloy.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.313-316
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• 2008

This work sought to examine the suitability of twin roll strip casting for Ag-27%Cu-25%Zn-3%Sn brazing alloy (BAg-7A) and to investigate the mechanical properties and microstructure of the strip. The effect of aging heat treatment on the properties was also studied,. This new manufacturing process has applications in the production of the brazing alloy. XRD and microstructural analysis of the Ag-27%Cu-25%Zn-3%Sn strip represented eutectic microstructure of a Cu-rich phase and a Ag-rich matrix regardless of heat treatment. The results of mechanical tests showed tensile strength of 470MPa, a significant enhancement, and an 18% elongation of the twin roll casted strip, due mainly to the solid solution strengthening of Zn atoms (${\sim}20%$) in the Cu-rich phases. Tensile results showed gradually decreasing strengths and increasing elongation with aging heat treatment. Microstructural evolution and fractography were also investigated and related to the mechanical properties.